LEPIDOPTERA (MOTHS AND BUTTERFLIES) AT INVERNESS RIDGE IN CENTRAL COASTAL CALIFORNIA AND THEIR RECOVERY FOLLOWING A WILDFIRE J. A. Powell Essig Museum of Entomology, University of California, Berkeley, CA 94720 Abstract.— In numbers of species, Lepidoptera (butterflies and moths) make up the largest group of plant-feeding animals in North America. Caterpillars of nearly all species feed on plants, and most of them are specialists on one or a few kinds of plants. Therefore they are liable to be severely affected by wildfires, and secondarily, their parasites and predators, including birds, bats, lizards, and rodents, suffer losses of a major food resource. In October 1995, a wildfire swept over part of The Point Reyes National Seashore, burning more than 12,300 acres (5,000 hectares) of public and private land, following a fire-free period of several decades. I tracked survival and recolonization by moths and butterflies during the subsequent five seasons. I made daytime searches for adults and caterpillars approximately monthly from March through October and collected blacklight trap samples, mostly in May and September-October. More than 650 species of Lepidoptera have been recorded in the Inverness Ridge area, and about 375 of them were recorded during the post-fire survey, including larvae of 31% of them. Plants in a Bishop pine forest higher on the ridge, where the fire was most intense, accumulated their caterpillar faunas slowly, while Lepidoptera feeding on plants typical of riparian woods in the lower canyons reestablished sooner and more completely. Recolonization varied markedly among different plant species, and the species richness gradually increased, in marked contrast to generalizations about effects of fire on arthropods derived from fire management of grasslands. Powell (2004) Lepidoptera at Inverness Ridge following fire Introduction Inverness Ridge forms the backbone of the Pt. Reyes Peninsula, located northwest of San Francisco Bay. The peninsula is defined by the San Andreas fault, running from Bolinas Lagoon through Olema Valley and Tomales Bay to the north. The long, straight ridge is situated along the eastern side of the peninsula, from about 15 miles NW of San Francisco, extending for about 20 miles (32 km). It is of relatively low relief, mostly 1000-1300 feet (300-400 m) elevation at the crest, broken only at Bear Valley by a low saddle of about 330 feet (100 m), then descends from Mt. Vision (1280 ft., 290 m) to low hills below 450 ft. NW of Inverness. The eastern front is quite steep, whereas the western slope is gradual, spreading out to the bluffs above Drakes Bay, the marshes of Drakes Estero, and the coastal downs and dunes of the Pacific Ocean shore of Pt. Reyes. East of the San Andreas fault the geological origin of mainland Marin County is very old, consisting of Franciscan sedimentary and igneous rocks of Jurassic origin. Formations of the Pt. Reyes Peninsula also are old but are granitic and originated far to the south, its terraine having moved northward along the fault during the Tertiary. As a result there are distinctive soils, plants, and insects that depend upon them, characteristic of both Inverness Ridge and areas east of the fault. Notably, redwood (Sequoia sempervirens) and associated communities are restricted to the Mt. Tamalpais region of Franciscan formations, whereas Bishop pine (Pinus muricata) is primarily a coastal species, dominant on Inverness Ridge, but occurs only sparsely on ridges of interior Marin County. Forests of Inverness Ridge also feature Douglas-fir (Pseudotsuga menziesii), madrone (Arbutus menziesii), coast live oak (Quercus agrifolia), tanbark (Lithocarpus densiflorus), and California bay (Umbellularia californica) on the east escarpment. On the west side there are groves of Bishop pine and live oak, downslope giving way to chaparral dominated by coyote brush (Baccharis pilularis), California coffeeberry (Rhamnus californica), and bush monkey flower (Mimulus aurantiacus), and gallery forests of alder (Alnus rubra) and willow (Salix lasiolepis) along the west flowing creeks. Nearly all collections of moths have been made in the northern half of Inverness Ridge in the vicinity of Inverness and Inverness Park, villages situated along the east side of the ridge, the southern half having been primarily private property until designation of Pt. Reyes National Seashore in 1965, when the land came under the jurisdiction of the National Park Service. Since that time there was no effort to inventory the Lepidoptera of the park until an extensive wildfire in 1995 led to a five-year survey on one transect, also on the northern half of the ridge. History of Lepidoptera Collections at Inverness Ridge There was no systematic and comprehensive baseline inventory of the moths and butterflies at any site on Pt. Reyes peninsula prior to the 1990s. There has been no long-term resident collector, although several persons made repeated one-night or short term visits between 1940 and 1965, collectively comprising a year-around sample at lights. Following is a chronicle of moth collectors who worked in the Inverness area, based on specimens examined, together with the primary locations of their specimens. [CAS= California Academy of Sciences, San 2 Powell (2004) Lepidoptera at Inverness Ridge following fire Francisco; EME= Essig Museum of Entomology, UC Berkeley; UCD = Bohart Entomological Museum, UC Davis; WDP = W. D. Patterson private collection, Sacramento] There is one specimen of Synanthedon sequoiae (Sesiidae) that was reared from Bishop pine at Inverness in 1916 by E. C. Van Duzee, who was a hemipterist and curator at the CAS, but I have not seen other Lepidoptera collected during that era. H. H. Keifer collected moths on at least two dates in 1926, while he was a curatorial assistant at the CAS, and there may be more of his specimens from Inverness for which data have not been retrieved. E. C. Johnston of Petaluma, CA, collected moths on at least four dates in 1938 and 1940, and presumably there were others, especially microlepidoptera in which he specialized. His private collection, however, went to the Canadian National Collection, Ottawa, after his death in the early 1950s, and he sent some specimens to the U.S. National Museum, Washington, but those collections have not been searched systematically to retrieve Inverness records. W. R. Bauer of Petaluma, CA, began making single night visits for macro moths in 1940. He continued following World War II, with 23 dates in 1947 and 21 in 1951. He was joined by J. S. Buckett beginning in 1954, and together they made collections during the following decade. Altogether Bauer worked at Inverness on more than 190 dates, mostly along Sir Francis Drake Highway and Pierce Point Road adjacent to Tomales State Park and at store front lights in Inverness, according to Bauer (1950s pers. comm.) and R. H. Leuschner, who collected with Bauer and Buckett in 1955. Cumulatively, they sampled on 15 or more dates in each month from February to July, but on fewer than 10 each month August to January (UCD). In addition they made many visits to McClures Beach on Tomales Point, but records from that locality and other beach dune sites on Pt. Reyes by many collectors are not summarized here. Buckett also collected microlepidoptera on his last visit, in 1965, providing the earliest known records for several species. Catherine Toschi (now Tauber) made sporadic collections of larger moths beginning in 1953 at the family summer home near Vision Rd. and collected through the summers in 1961-62, while working as a student assistant in the museum at UC Berkeley, and on several dates in 1963-64, including a few in February. Her efforts, comprising a total of more than 60 dates, provided the first large-scale survey of small moths (EME). W. D. Patterson also collected larger moths and butterflies in Inverness in the mid 1950s and subsequently on sporadic visits, emphasizing microlepidoptera as well since 1995, at a family summer home near the top of Perth St. (WDP). C. W. O’Brien collected small moths on about 25 dates during1959-63 at a site 1 mile SE of Inverness, near Dream Farm Rd. (EME). These were mostly in October to February and produced the earliest records of several microlepidoptera. P. A. Opler made the first larval collections on Inverness Ridge during several visits in 1967-69, in association with his research on microlepidoptera of coast live oak; I participated twice, and we collected larvae from a few other plants and wood rot fungi (EME). D. S. Green also sampled leaf mines, primarily on oak, making monthly visits between August 1976 and May 1977 (EME). I made single night visits to the Inverness area with D. D. Linsdale in January 1959 and February 1961, and for several years beginning in 1970 participated in annual visits in May by a field 3 Powell (2004) Lepidoptera at Inverness Ridge following fire entomology class from the UC Berkeley, led by E. I. Schlinger. We camped atop Inverness Ridge in the area of the western terminus of Drakes View Road and ran blacklight sheets 2 nights each year and had phenomenally good luck with warm, calm evenings, unusual for May, in 1970 and 1972. Hence, a large number of persons contributed to a brief seasonal sample. In addition to adults taken diurnally and at black lights, I made about 40 larval collections (EME). Beginning in1994 my wife, Liz Randal, and I began making longer-term visits, and I started systematically recording all Lepidoptera species. Ultimately, I sampled moths at lights on about 220 dates between July 1994 and December 2001,. These data originated from several sites — July 1994 (7 dates) and May 1995 (7) in the Sea Haven district near Tomales State Park; Jan.- Feb. 1995 (28), Oct. 1997 (28), Sept.-Oct.